1. Field of the Invention
The present invention relates to a process for preparing agglomerates of N-[N-(3,3-dimethylbutyl) -L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester (also known as neotame) and a carrier. The invention also relates to the novel agglomerates.
2. Discussion of the Related Art
N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester is a derivative of aspartame that has a sweetening potency that is about 40 to 50 times that of aspartame (and about 8,000 times that of sucrose). N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester may be prepared from aspartame as described in U.S. Pat. No. 5,480,668, U.S. Pat. No. 5,510,508, and U.S. Pat. No. 5,728,862, all of which are incorporated by reference herein.
Structurally, N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester and aspartame differ in that, in N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester, a bulky neohexyl substituent is present on the amine nitrogen. ##STR1##
This structural difference results in dramatic differences in the physical and chemical properties of these compounds. For example, the melting point of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester is about 82.2.degree. C., while that of aspartame is 248.degree. C. In addition, N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester has much higher solubility in organic solvents than aspartame. It is also known that N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester has a higher stability than aspartame under some pH conditions, as described in U.S. Pat. No. 5,480,688. The pronounced difference in sweetness between the two compounds is further evidence of their chemical dissimilarity.
The solubility of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester in water is about 1%, which is approximately equal to the water solubility of other high intensity sweeteners such as aspartame. However, while the solubility of other high intensity sweeteners in ethanol is very low (e.g., less than 0.1% for aspartame), the solubility of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester in ethanol is greater than 100g/100ml.
Thus, unlike less soluble sweeteners such as aspartame which are agglomerated as a powder onto a powder carrier, N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester may be agglomerated as a solution onto a powder carrier. The process of agglomeration using a N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester solution, rather than a powder, provides numerous significant advantages including improved content uniformity and ease of processing.
N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester may be used for sweetening a variety of products, including drinks, foods, confectionery, pastries, chewing gums, hygiene products and toiletries, as well as cosmetic, pharmaceutical and veterinary products. Its superior sweetening potency makes N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester an attractive alternative to aspartame because it permits the use of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester in substantially smaller quantities than is required for aspartame to achieve an equivalent sweetening effect.
Because of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester's superior potency, it is convenient to prepare compositions of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester which deliver sweetness on par with that of aspartame. For liquid products such as beverages, this may be accomplished by preparing dilute solutions of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester. Since N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester's sweetening potency is about 40 times greater than that of aspartame, these solutions can be prepared using about 2.5% as much N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester as would be required to prepare solutions of equal sweetness using aspartame. This amount can be adjusted to take into account the relative potency differences relating to the concentration effect of the respective sweeteners.
For solid products, such as tabletop sugar substitutes, this may be accomplished by forming a dry blend of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester with a bulking agent such as, for example, Unidex brand mixture of dextrose (97%) and maltodextrin (3%) available from CPC International. It is common to blend 95% by weight Unidex with 5% by weight aspartame to provide a tabletop sugar substitute. An equivalent N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester sugar substitute would require blending about 99.875% by weight Unidex with about 0.125% by weight N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester.
The use of small amounts of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester powder to prepare dry blends with a bulking agent presents several manufacturing difficulties. Not surprisingly, dry blends prepared using a relatively small amount of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester and a relatively large amount of a bulking agent may exhibit poor content uniformity. Because of the relatively small amount of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester as compared to bulking agent, these dry blends also may exhibit a high degree of segregation and dusting. Moreover, the content uniformity and segregation problems associated with such dry blends often worsen during shipping and also during periods of storage. Consequently, these dry blends may be somewhat unattractive for manufacturers of consumer products as well as for consumers.
It would be highly desirable to overcome the difficulties described above by preparing agglomerates of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester with a carrier and using the agglomerates to provide N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester in a deliverable form. In addition, it would be extremely advantageous to provide a tabletop sweetener with agglomerates of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester. Similarly, it would be extremely advantageous to provide a powdered soft drink mix with agglomerates of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester. It is also important to deliver a blend of sweetness in an efficient manner.
Fluidized bed agglomeration is well known in the art. The process is described in U.S. Pat. Nos. 2,856,290, 3,251,695, and 3,433,644, the disclosures of which are incorporated by reference herein. Typically, in both continuous and batch fluid bed agglomeration processes, finely divided particles are sprayed onto a fluidized bed of particles under moisture and temperature conditions which promote formation of an agglomerate. Often the process involves heating at least one of the components of the agglomerate to a temperature above its melting point.
U.S. Pat. No. 4,554,167 discloses a method for preparing agglomerates of aspartame and acid-containing food mixes. The disclosed agglomeration process does not involve heating one or more of the agglomerate components to a temperature above its melting point. Neither does the disclosed process involve dissolving the high intensity sweetener in a solvent prior to formation of the agglomerate.
Agglomerates of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester would facilitate adjustment of the amount of N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester to be delivered. These agglomerates also would provide N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester preparations with excellent content uniformity. In addition, these agglomerates also would exhibit reduced segregation and dusting as compared to the N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine 1-methyl ester dry blend preparations.